The present invention relates to an idling stop technique for automatically stopping/starting an engine of a vehicle.
In recent years, from the viewpoint of reduction in fuel consumption, exhaust gas, or the like, an idling stop device has come into practical use which automatically stops/starts an engine of a vehicle when the vehicle is stopping for a comparatively short time, for example, at the time of waiting for a traffic signal to change. In a vehicle having an idling stop device, if a stop condition is established, for example, if a brake pedal is pressed in a traveling state and the vehicle is in a stop state, the engine is automatically stopped. When the engine is stopped, if a start condition is established, for example, if the brake pedal is released, the engine is automatically started (for example, see JP-A-2009-13953).
Power which drives a starter motor for starting the engine of the vehicle is supplied from a battery in the vehicle. Very large power is required when the starter motor starts the engine. For this reason, when the voltage of the battery is reduced, if the engine is repeatedly stopped and started through an idling stop function, the voltage of the battery is further reduced, causing a problem in that the engine may not be started. Thus, when the battery is deteriorated and the voltage of the battery is reduced, it is necessary to take a countermeasure which ensures that the engine can be started.
On the other hand, as described above, since very large power is required when the starter motor starts the engine, in starting the engine, the voltage of the battery is significantly reduced. For this reason, for example, a microcomputer in the idling stop device is configured to monitor the voltage of the battery when the engine is started by a user's manipulation of a start switch. When the voltage of the battery at this time is reduced less than a predetermined threshold value, in subsequently starting the engine through the idling stop function, the microcomputer is configured to carry out a countermeasure which ensures that the engine can be started.
However, since power for actuating the microcomputer is supplied from the battery, in starting the engine, when the voltage of the battery is significantly reduced less than a voltage at which the microcomputer is actuated, the microcomputer itself cannot be actuated and is reset. The microcomputer which has been reset and rebooted cannot recognize the reason for resetting or the voltage of the battery before resetting. The microcomputer is reset, for example, in a runaway state or the like, in addition to the reduction in voltage of the power supply, but the reason for resetting cannot be recognized.
For this reason, even when the voltage of the battery is significantly reduced and the microcomputer is reset, the microcomputer after resetting does not take a countermeasure which ensures that the engine can be started, but starts the engine through the idling stop function. As a result, the microcomputer may be again reset and the engine may not be started.